The present invention disclosed herein relates to a Radio Frequency IDentification (RFID) system, and more particularly, to an RFID reader and a method for suppressing transmission leakage signals thereof.
Radio Frequency IDentification (RFID) is a technology that uses radio waves to identify information. An RFID system includes an RFID tag and an RFID reader.
In general, an RFID reader uses one or two antennas to transmit/receive signals.
An RFID reader using one antenna divides a transmit (TX) signal and a receive (RX) signal by a directional coupler. The directional coupler transfers a TX signal, received from a transmitting unit, to the antenna and prevents the TX signal from being transferred to a receiving unit. Also, the directional coupler transfers an RX signal, received from the antenna, to the receiving unit and prevents the RX signal from being transferred to the transmitting unit. However, in general, the TX/RX isolation of the directional coupler is not high. Thus, the TX signal leaks through the directional coupler toward the receiving unit (i.e., an internal leakage signal). Also, a portion of the TX signal transferred to the antenna is reflected toward the directional coupler. The reflected signal (i.e., an external leakage signal) is transferred through the directional coupler to the receiving unit, despite being a signal received from the antenna.
In the case of an RFID reader using two antennas, a TX signal outputted from the TX antenna is transferred through the RX antenna to a receiving unit. As the size of the RFID reader decreases, a leakage signal (i.e., an internal leakage signal) transferred to the receiving unit increases because the distance between the TX/RX antennas decreases. Also, in the case of the RFID reader using two antennas, a portion of the signal transferred to the antenna is reflected toward the RX unit. The reflected signal (i.e., an external leakage signal) is transferred through a directional coupler to the receiving unit, despite being a signal received from the TX antenna.